1. Field of the Invention
The present invention relates to a liquid crystal display device, in particular, to an orientation division type liquid crystal display device of which the manufacturing process is simplified.
2. Description of the Related Art
Conventional liquid crystal display devices are widely known in which a twisted nematic system or a vertical orientation system are adopted. However, liquid crystal display devices of those systems have the problem that the tint differs according to the viewing angle, since the orientation direction of the liquid crystal molecules of the intermediate layer of the liquid crystal layer at the time of voltage application is uniform within pixels and, therefore as a method to improve this viewing angle characteristic, an orientation division type liquid crystal display device is introduced. Here, the orientation division type liquid crystal display device is a technology for gaining broad sight angle characteristics by dividing one pixel into a plurality of regions and by making the orientation direction of the liquid crystal molecules of the intermediate layer in each region different, so that the visual characteristic of each region compensate for each other.
FIG. 1 is a sectional view showing an orientation division type liquid crystal display device according to a prior art (conventional example 1: for example Japanese Laid-open Patent publication No. Hei-10-20323) and FIG. 2 is a plan view of the same.
As shown in FIG. 1, a switching element comprises a gate electrode 403, a gate insulation film 404, a semiconductor layer 405, a drain electrode 406 and a source electrode 407. The switching element and a pixel electrode 408 which is electrically connected to the source electrode 407 are arranged on a substrate 401. An opening 409 is provided to the pixel electrode 408 which becomes the border of the regions for orientation division. Under the opening 409, a control electrode 411 is provided. The numeral 424 shows a passivation film and the 425 shows a color layer. Also, the numerals 426 and 427 show optical films.
On the opposite substrate 402, a common electrode 412 is provided. This common electrode 412 doesn""t need an opening. Orientation films 413 and 414 are formed on the respective substrate 401 and 402, as the top layers of the respective substrates, and the orientation films 413 and 414 sandwich liquid crystal molecules 415. By applying a voltage onto the control electrode 411, a diagonal electric field is generated across the edge of the opening 409 and the edge of pixel electrode 408. The orientation direction of the liquid crystal molecules 415 is divided by the diagonal electric field of which the direction of the generation differs with the border of the opening 409.
The orientation direction of the liquid crystal molecules as shown in FIG. 1 exhibits the orientation direction of the liquid crystal molecules 415 existing mainly in the central layer of the liquid crystal molecule layer. At this time by carrying out ultraviolet irradiation, a small amount of ultraviolet curing monomer or oligomer, which has been added to the liquid crystal molecules 415 in advance, is polymerized to become a polymer 416.
The polymer 416 follows the orientation direction of the liquid crystal molecules 415 at the time of ultraviolet irradiation so as to secure its form even in the case when no voltage is applied to the control electrode 411. In addition, since the polymer 416 is small in quantity, the liquid crystal molecules 415 are regulated only in the rising direction at the time of voltage application while the gradient changes according to the applied voltage. Accordingly, it is not necessary to apply a voltage to the control electrode 411 at the time of driving and the display can be made performed by only applying voltage to the pixel electrode 408, with the result in that application only to the pixel electrode 408 makes display possible.
In the plan view as shown in FIG. 2, an example is disclosed in which the structure is formed in a Y shape configured by the opening 503 and the control electrode 501 arranged side by side. When carrying out a predetermined rubbing and when performing the process of the above described orientation division, a TN orientation divided into four pieces is formed by this configuration.
In an example with respect to the control electrode in this disclosed technology there are descriptions in which the control electrode is formed in the same layer as the gate electrode, in which a different voltage from that of the pixel part can be applied to from the outside, and in which a voltage is applied to the control electrode at the time when the device is manufactured. However, there are no descriptions with respect to its wiring method and how to draw out terminals.
Technologies where the control electrode is added in order to carry out an orientation control of the liquid crystal molecules such as the technology described in the Japanese Laid-open Patent publication No.Hei-10-20323 of the conventional example 1 are also disclosed in the Japanese Laid-open Patent publication No.Hei-7-13164, the Japanese Laid-open Patent publication No.Hei-7-199190, the Japanese Laid-open Patent publication No.Hei-7-230097 and the Japanese Laid-open Patent publication No.Hei-8-76125. The particular points of difference between these technologies and the technology of conventional example 1 is that a predetermined voltage is applied not at the time when the device is manufactured but at the time the display is driven.
FIG. 3 is a plan view showing a technology disclosed in the Japanese Laid-open Patent publication No.Hei-7-199190 (conventional example 2).
Referring to FIG. 3, the control electrode 601 (referred to as an orientation control electrode in the above described publication) has a structure which surrounds the periphery of the pixel electrode 602 so as to control the orientation direction of the liquid crystal molecules by generating a specific diagonal electrical field between each edge of the pixel electrode 602 and the control electrode 601. There are mainly two types of settings with respect to the positional relationships of each electrode and an applied voltage. The first setting is an electrode arrangement where the control electrode is arranged as the lower layer of the pixel electrode and an X type opening 603 is arranged in the common electrode on the opposite substrate. In this structure, the control electrode is connected in parallel to the input terminal of the common electrode and is set to be at the same potential as the common electrode. The second setting is an example where the X type electrode opening 603 is arranged in the pixel electrode 602 so that the control electrode 601 is arranged as a layer above the pixel electrode.
Regarding the applied voltage settings in this structure, there is a description in which the effective potential difference between the control electrode and the common electrode is set to be larger than the effective potential difference between the display electrode and the common electrode without any description relating to its wiring or the way the terminal are drawn out. That is to say, there is no description with respect to the connection structure in the case where a different potential independent of the pixel electrode or the common electrode is applied to the control electrode. With respect to this point the situation is the same as that in the Japanese Laid-open Patent publication No.Hei-7-13164 and the Japanese Laid-open Patent publication No.Hei-8-76125.
Next, referring to FIG. 4, a technology described in the Japanese Laid-open Patent publication No.Hiei-7-230097 (conventional example 3) is explained. Referring to FIG. 4 the control electrode 701 arranged in each pixel is connected to the gate wiring 704. By this structure, the same potential as that of the gate wiring 704 and the gate electrode 703 is applied to the control electrode 701 in the configuration.
As described above, with respect to a liquid crystal display device where a voltage is applied to the control electrode at the time when the display is driven, a structure is disclosed where a voltage is applied by connecting the control electrode to the common electrode or the gate electrode.
In the case of each of the above described conventional examples, however, the potential of the control electrode becomes a potential specified as the same potential as the common electrode or the gate electrode. Therefore, it is difficult to set the diagonal electrical field for controlling the orientation direction of the liquid crystal molecules to the optimal dimension. It is also necessary to construct the control electrode which enables this optimal diagonal electrical field to be set easily.
The object of the present invention is to provide an orientation division type liquid crystal display device of which the manufacturing method is simplified.
A liquid crystal display device according to the present invention comprises two substrates of glass or the like, a liquid crystal layer sandwiched between said substrates and a gate terminal (105), a gate wiring (104), a control electrode (101) and a drain terminal (107) are arranged on the liquid crystal layer. The liquid crystal display device further comprise a control electrode terminal of the control electrode in a condition independent of the gate wiring so that the configuration is characterized in that the terminal part including this control electrode terminal, the gate terminal and the drain terminal is arranged on the outer side of the substrate panel.
In the liquid crystal display device, the control electrode terminal may be arranged so as to be extended to the terminal part where the drain terminal exists after each control electrode is connected to one line on the external side which is the opposite side to the side where the gate terminal (105) is arranged and which does not cross the gate wiring (104). The terminal part may be arranged onto the two outer sides of the substrate panel.
The control electrode terminal may be provided for each row on the outer side of the substrate panel which is a different side from where the gate terminal is arranged.
The control electrode terminal may be provided to the layer which is the same as, or different from, the layer where the gate wiring and/or the gate terminal are arranged.
The control electrode may have a lattice type structure including a structure where two Y shapes are combined.
A voltage independent from other terminals including the gate terminal and drain terminal, may be applied to the control electrode terminal at the time when the liquid crystal display device is manufactured and/or at the time of driving so that it becomes possible to regulate the rising direction of liquid crystal molecules in the liquid crystal layer.
In the above described liquid crystal display devices according to the invention, the control electrode terminal of each control electrode is arranged on the outer side which does not cross the gate wiring and the terminal parts, including the gate terminal, the drain terminal and the control electrode terminal are arranged on the outer side of the substrate panel.
In this configuration, an arbitrary voltage can be applied to the control electrode so that the diagonal electrical field which is necessary for orientation division can be set to optimal intensity. Therefore, the orientation division can be carried out properly. In addition, since there is no overlapping between the control electrode (including wiring and terminals) and the gate wiring, the short circuit problem can be improved so as to create good manufacturing yield of the liquid crystal display device. Moreover, the terminal parts can be composed of two sides of the panel allowing a minimized area of the non-display part, despite the drawing out of more terminals than in the general liquid crystal display device. Therefore, the panel""s outer shape can be made small. In addition, it becomes possible to arrange the gate terminal and control electrode terminal on the same side so that it becomes unnecessary to be arranged with division in the case when using a driver which has the output for the gate electrode and the output for the control electrode together. Therefore, the number of drivers can be made smaller so as to reduce the process steps for attaching the driver.